Japan’s Osaka struggled to find her rhythm throughout the contest, making 66 unforced errors, and had tears in her eyes midway through the second set with the match slipping away.

She fought back, however, and eventually proved too strong for her Chinese opponent, prevailing in two hours and 33 minutes.

“She is such an incredible player and it was really hard to play against her here. I’m just thinking one match at a time, and it can only get harder from here,” said Osaka, who cried following her U.S. Open win that was overshadowed by Serena Williams’ altercation with umpire Carlos Ramos.

Zhang raced into an early lead and held firm to clinch the opening set comfortably. The 29-year-old went 2-0 up in the next to raise hopes of an upset victory.

Osaka battled with her emotions but held her nerve to save two break points before dragging the contest into a decider.

Zhang, however, refused to back down and went up 4-1 before Osaka switched gears to close out the victory.

“I was sort of apologizing for my behavior because I was kind of stressed,” Osaka said when asked what the pair spoke about at the net following the match.